Lawn and garden vehicles such as riding lawn mowers, lawn tractors, garden tractors and other similar vehicles commonly include a hydrostatic transmission, and a foot pedal or control lever is provided for controlling the speed of operation of the vehicle. In most such constructions the operator must maintain a constant uniform pressure on the pedal if the vehicle is to move at a consistent speed. In such vehicles the force which the operator must apply on the foot pedal may be substantial when the vehicle is operated under high drawbar load conditions such as during plowing or towing a trailer or loaded grass catcher etc. Maintaining a constant force on the foot pedal may become very tiring to the operator.
Some prior art constructions have used speed control assemblies where there is sufficient friction in the control assemblies to maintain a control level or foot pedal in position even under high drawbar load conditions. These prior art structures have the disadvantage of requiring substantial force to change travel speed.
Other prior art constructions have employed electric clutch arrangements which can be energized to apply friction drag to the control mechanism to maintain constant travel speed. During operation of a lawn and garden vehicle, it is commonly desireable that the speed of the vehicle be set at a constant speed, such as for plowing. At the end of a row, the operator lifts the plow and then accelerates while turning the vehicle. The speed control arrangement should permit the operator to establish a proper minimum speed, e.g. for plowing, then permit the operator to accelerate, and then return to the original speed setting. In the prior art apparatus employing an electric clutch, the operator must apply a substantial force on the foot pedal to override the speed control when the electric clutch is engaged. When the operator overrides the electric clutch, he sets the control at a new speed setting. Those constructions do not permit the operator to then return to the original minimum speed setting by merely releasing the speed control. In order to return to the original selected speed with vehicles including an electric clutch, the operator must again apply a substantial force to the speed control lever or pedal to once again set the speed.